Fluorine free lithium ion batteries using aqueous polymeric binders

Abstract

Electric vehicles have become the focal point to reduce GHG in the quest for cleaner and more efficient means of transportation. At the core of this transition lies the key component of energy storage, the battery pack. The battery pack has electrodes manufactured with the binder PVDF. Using fluorine-rich compounds makes processing and recycling a more difficult process and it is also harmful for the environment. Therefore, alternative binders should be explored to adhere to the principles of sustainability. In this thesis, a comparative study is presented between electrodes fabricated with fluorine free polymeric binders and PVDF. Moreover, a battery cell solely constituted of fluorine free components is fabricated and tested. By using the analysis techniques electrochemical performance testing, electrochemical impedance spectroscopy and scanning electron microscopy the effect of the binders and electrolytes on the electrode performance is explored. The findings reveal that during rate performance cycling, graphite half cells based on the binder PAA demonstrated the highest discharge capacities at C-rates up to 4C with a capacity retention of 39%. NMC811 half cells based on a composite binder CMC/SBR achieved the highest capacity retention after 100 cycles, being 24%. All the fabricated full cells suffered from a 30-40% initial capacity depletion after the first charge, presumably originating from oxidative degradation of the electrolyte. Consequently, the highest capacity retention after 150 cycles was 14% for a PVDF based full cell. Fluorine free cells using a PAA anode and CMC/SBR cathode exhibited expected capacities with a higher overpotential.